The present invention relates to a water jet propulsion type outboard motor, in particular, to an improvement of a water anti-splash device also serving as a water intake unit for cooling water, an exhaust system for reducing exhaust noise, and a movable screen.
Japanese Patent Application Laid-Open NO.9 (1997)-309492 discloses a water jet propulsion type outboard motor including an impeller that is housed within a duct having a suction port and a nozzle: water sucked from the suction port is pressurized the impeller to be jetted out from the nozzle to propel a ship. However, since the impeller of this outboard motor consists of axial flow blades, a thrust obtained with such an impeller is limited. Moreover, since the pressurized water in the duct is used as cooling water for an engine, sand flowing through the suction port gets mixed in with the cooling water for the engine.
Japanese Patent Application Laid-Open NO.11 (1999)-286297 discloses a splashproof device for an outboard motor, in which a horizontal plate type splashboard is provided between the outboard motor and a ship so as to prevent an increase in running resistance caused by water striking against the outboard motor as well as to prevent water from splashing into the ship. However, this splashproof device is not capable of preventing water splashing from the stern from striking against a side face of the outboard motor when the outboard motor is rotated to change the running direction. Therefore, this splashproof device cannot prevent resistance from being increased. Moreover, water striking against the side face of the outboard motor splashes into the ship.
Japanese Patent Application Laid-Open NO.9 (1997)-39892 discloses a water jet propulsion type outboard motor, in which a swirl water flow pressurized with an impeller is conveyed to a volute casing to be jetted out from a discharge port so as to propel a ship. However, since this outboard motor vertically sucks water from a suction port, there is a possibility that cavitation may occur due to negative pressure at the suction port while the ship is running. Moreover, exhaust gas from an engine is directed to an underwater exhaust chamber, to which high-pressure water in the volute casing is supplied, so that energy of the exhaust gas is absorbed by the water so as to deaden the noise. However, since the high-pressure water is supplied to the underwater exhaust chamber through a hole provided through the volute casing, energy loss is generated.
Japanese Patent Application Laid-Open NO.8 (1996)-253196 discloses a screen for debris removal, which is fixed over an inlet port of a suction casing so as to prevent debris floating under the water and on the water surface from being sucked inside. However, since this screen is fixed, it is necessary to remove screws, pins or the like which fix the screen in order to remove debris such as vinyl or cords passing through the screen and caught on an entry section of an impeller. Therefore, it is difficult to remove debris when a ship is on the water.
In view of the conventional problems as described above, the present invention has an object of providing a small and light-weight safety water jet propulsion type outboard motor with high propulsion efficiency.
Another object of the present invention is to provide a water intake unit for preventing sand or the like from getting mixed with cooling water, an anti-splash device for preventing an increase in running resistance due to collision of a water flow splashing from a stern against a propulsion device and for preventing water from splashing into a ship, an exhaust system for reducing exhaust noise to lower the operation noise, and a movable screen for facilitating the removal of debris or the like.
In order to achieve the above objects, a water jet propulsion type outboard motor according to a first aspect of the present invention includes: a power source; a driving system for transmitting a driving power of the power source; a curved tubular duct member fixed to a housing on which the power source is mounted, having a suction port and a discharge port; guide blades provided within the duct member, in the vicinity of the discharge port thereof; and an impeller enclosed by the duct member and rotated by the driving system, wherein an outer peripheral edge of a spiral blade of the impeller provided around its hub is close to an inner peripheral face of the duct member, and an outer peripheral distal end portion of the impeller extends toward the suction port.
In the above structure, since the impeller is enclosed within the duct member for protection, the impeller does not come into contact with obstacles such as sand or rocks. Therefore, according to the outboard motor including the impeller, the safe running of a ship can be provided even in shallows such as in the vicinity of a shoreline or on a river.
Moreover, since the duct member has a curved tubular shape, a length of the duct member can be reduced, thereby reducing the outboard motor in size as well as in weight. Therefore, since the outboard motor does not protrude backward from the ship, the amount of band-shaped objects caught on the outboard motor or the contact with the driftwood or the like is decreased, thereby increasing the working rate and enhancing the safety of the outboard motor.
Since the outer peripheral edge of a spiral blade is close to an inner peripheral face of the duct member so as to give an axially symmetrical energy to a fluid in a cross section vertical to a rotation axis of the impeller, balance efficiency is improved. Moreover, the outer peripheral distal end portion of the spiral blade extends to the side of the suction port to form wide suction port and flow path of the impeller, floating objects are not caught on the spiral blade even when the floating objects flow into the duct member. Moreover, even when string or the like flows into the duct member, the string does not wind itself around the long blade face of the spiral blade. As a result, the suction performance is improved.
A water jet propulsion type outboard motor according to a second aspect of the present invention is the outboard motor of the first aspect, wherein the outboard motor further includes a cooling water system for cooling the power source, including: a pump for pumping up water from outside; first and second water channel systems for guiding water from outside into the pump; and a third water channel system from the pump via the power source to the outside.
A water jet propulsion type outboard motor according to a third aspect of the present invention is the outboard motor according to the second aspect, wherein the first water channel system includes: a water suction port provided on an inner surface of the duct member between the impeller and the discharge port; a straight tubular path having the water intake port on its end, penetrating through the duct member; a first water channel branching from the straight tubular path, for guiding water into the pump; and a strainer provided in the straight tubular path so as to be detachable from the outside, and wherein the second water channel system includes: a water intake unit for taking in water from outside; and a second water channel for guiding water from the water intake unit into the pump.
In the above structure, the cooling water system for cooling the power source includes two water channel systems for guiding cooling water into the pump, that is, the first and second water channel systems. The first water channel system takes water in through the water intake port provided on the inner wall of the duct member between the impeller and the discharge port, whereas the second water channel system takes water in from outside. During the normal running of the ship, water pressure within the duct member between the impeller and the discharge port is increased by the rotation of the impeller. Thus, the cooling water is mainly taken from the water intake port of the first water channel system. During the running of the ship in shallows, even when sand or the like is sucked into the duct member so as to cause clogging of the strainer provided for the straight tubular path extending from the water intake port, making it difficult to take water in through the water intake port of the first water channel system, water is continuously supplied to the cooling water system because the pump takes water in from the water intake unit of the second water channel system instead. Thus, the burning out of the power source can be prevented.
Moreover, since the strainer is provided in the straight tubular path penetrating through the duct member, the strainer is detachable from outside.
A water jet propulsion type outboard motor according to a fourth aspect of the present invention is the outboard motor of the second aspect, wherein the outboard motor includes a water supply port for supplying running water to the first and second water channel systems.
In the above structure, water can be supplied from the water supply port to the first and second water channel systems. Therefore, when the running water is connected to the water supply port during washing operation on land, running water can be easily supplied to the cooling water system to wash the power source of the cooling water system (for removal of a salt content, mud, sand or the like) and to cool the bearings of the impeller.
A water jet propulsion type outboard motor according to a fifth aspect of the present invention is the outboard motor of the third aspect, wherein the outboard motor propels with the water intake unit of the second water channel system being juxtaposed with the inlet port of the duct member.
In the above structure, since the water intake unit is juxtaposed with the suction port, the water intake unit is not affected by the suction of sand or the like into the duct member during the running of a ship.
A water jet propulsion type outboard motor according to a sixth aspect of the present invention is the outboard motor of the third aspect, wherein the water intake unit of the second water channel system comprises an expanded water channel wider than the second water channel.
In the above structure, since the water intake unit has an expanded water channel which is wider than the second water channel, water flowing into the water intake unit circulates and is retained within the expanded water channel before it can be sucked into the second water channel. At this time, sand or the like mixed with the flowing water precipitate within the expanded water channel to be separated from the water.
A water jet propulsion type outboard motor according to a seventh aspect of the present invention is the outboard motor of the sixth aspect, wherein the water jet propulsion type outboard motor includes: an expanded water channel shell defining the expanded water channel; and a flat plate protruding outward from the expanded water channel shell, wherein the outboard motor propels with the flat plate being provided horizontally in the vicinity of the water surface.
In the above structure, since the flat plate protrudes outward from the expanded water channel shell and is horizontally provided in the vicinity of the water surface, the flat plate blocks a flow of splashing water so as to prevent water from splashing into a ship. Moreover, the flat plate reduces a running resistance of the ship so as to prevent the running speed from being lowered.
A water jet propulsion type outboard motor according to an eighth aspect of the present invention is the outboard motor of the seventh aspect, the expanded water channel shell is provided with: a first opening for taking in water from outside; and a second opening communicated with the second water channel, wherein the outboard motor propels with the first opening being oriented downward.
In the above structure, since the first opening of the expanded water channel shell is oriented downward, debris or the like do not easily flow into the water intake unit while the ship is running.
A water jet propulsion type outboard motor according to a ninth aspect of the present invention is the outboard motor of the eighth aspect, wherein a strainer is attached over the first opening.
A water jet propulsion type outboard motor according to a tenth aspect of the present invention is the outboard motor of the eighth aspect, wherein the expanded water channel shell includes a pipe protruding inward provided on the second opening.
In the above structure, since a strainer is attached over the first opening, debris or the like is removed from water flowing into the water intake unit. Moreover, when a tip of the pipe protruding inward provided on the second opening of the expanded water channel shell is placed in a stagnant flow region within the expanded water channel, water without sand or the like can be efficiently taken in.
A water jet propulsion type outboard motor according to an eleventh aspect of the present invention is the outboard motor of the first aspect, wherein the outboard motor further includes an exhaust system for discharging exhaust gas from the power source to the outside, including: a first exhaust system provided within the housing, connected to the power source; and a second exhaust system for guiding exhaust gas to the outside, connected to the first exhaust system.
A water jet propulsion type outboard motor according to a twelfth aspect of the present invention is the outboard motor of the eleventh aspect, wherein the second exhaust system includes: an exhaust path provided around a surrounding wall of the duct member, connected to the first exhaust system; and an exhaust port in the vicinity of the discharge port of the duct member, wherein the outboard motor propels with the exhaust port being provided under the discharge port.
In the above structure, since the exhaust port is open in the vicinity of a lower side of the discharge port, the exhaust gas from the power source is released under water. A pressure fluctuation of the exhaust gas (exhaust noise wave) of the power source is dissipated so as to be attenuated while the exhaust gas is passing through the water. Therefore, exhaust noise of the power source is reduced.
A water jet propulsion type outboard motor according to a thirteenth aspect of the present invention is the outboard motor of the twelfth aspect, wherein the second exhaust system further includes a nozzle portion connected from the exhaust path to the exhaust port along the duct member, and wherein the outboard motor propels with the nozzle portion being provided on a bottom of the duct member.
In the above structure, since the nozzle portion is provided along the bottom of the duct member, the side slipping of a ship is prevented, thus enhancing the straight running ability of the ship.
A water jet propulsion type outboard motor according to a fourteenth aspect of the present invention is the outboard motor of the eleventh aspect, wherein the second exhaust system includes: a plurality of expansion chambers connected to the first exhaust system; and an exhaust pipe connected to the expansion chamber, for discharging exhaust gas to the outside.
In the above structure, when exhaust gas from the power source successively flows into a plurality of expansion chambers to be repeatedly expanded therein, and pressure fluctuation of the exhaust gas (exhaust noise wave) is gradually attenuated. Thus, exhaust noise of the power source is reduced.
A water jet propulsion type outboard motor according to a fifteenth aspect of the present invention is the outboard motor of the eleventh aspect, wherein the outboard motor further includes a cooling water system for cooling the power source, including: a water supply system for supplying water from outside into the power source; and a draining system for draining water from the power source to the outside, wherein the draining system and the exhaust system include a sump chamber for storing water from the draining system, and exhaust gas from the power source passes through the water stored in the sump chamber.
In the above structure, when the exhaust gas from the power source passes through the water stored in the sump chamber, pressure fluctuation of the exhaust gas (exhaust gas wave) of the engine is dissipated, so that in particular, higher harmonic waves (transmitting sound) is attenuated. Therefore, exhaust noise of the engine is reduced, and the operation noise is lowered.
A water jet propulsion type outboard motor according to a sixteenth aspect of the present invention is the outboard motor of the fifteenth aspect, wherein the water supply system is provided with a water supply port for supplying running water.
In the above structure, if running water is supplied from the water supply port, water can be stored in the sump chamber. Thus, similar sound deadening effects as those obtained during the running of the ship can be obtained even during the washing operation on land.
A water jet propulsion type outboard motor according to a seventeenth aspect of the present invention is the outboard motor of the first aspect, wherein the outboard motor further includes: a screen swingably supported on a peripheral of the suction port; a flexible lever connected with the screen; and an engaging slot to be removably engage with the lever; and wherein the outboard motor propels with the suction port of the duct member being oriented downward and a swing pivot of the screen being provided on a side of forward running.
In the above structure, when the lever is disengaged from the engaging slot so that the screen is separated from the suction port during the running of a ship, debris or the like caught on the screen can be swept away by a water flow caused by the running of the ship. If the lever is engaged with the engaging slot in a deflected state, the screen can be pushed against the inlet port to be attached thereon.